A variety of aqueous electroplating baths and processes are known in the art and are in widespread commercial use for electrodepositing a nickel-iron alloy on electrically conductive substrates. Such nickel-iron alloy deposits possess excellent corrosion resistance and are particularly useful for providing decorative finishes on corrosion susceptible substrates over which a subsequent electrodeposit of chromium is applied. It is extremely important that such nickel-iron decorative deposits are characterized by their high-leveling properties, exceptional brightness and good ductility and that these beneficial characteristics are uniform over the entire electrodeposit.
Typical of known nickel-iron electroplating bath compositions and processes are those described in U.S. Pat. Nos. 3,354,059; 3,795,591; 3,806,429; 3,812,566; 3,878,067; 3,974,044; 3,994,694; 4,002,543; 4,089,754; 4,101,387; 4,134,802 and 4,179,343. While certain of the nickel-iron plating bath compositions and processes as described in the aforementioned United States Patents have provided satisfactory electrodeposits for use in decorative applications, a continuing problem associated with such and other nickel-iron plating baths is their susceptibility or sensitivity to contaminants and organic degradation products formed during prolonged use of such baths detracting from the character and properties of the electrodeposit. This problem is particularly pronounced in electroplating baths designed to electrodeposit alloys containing high percentages of iron, such as for example, alloys containing above about 35% iron and operating at a pH above about 3.4. The progressive contamination of such electroplating baths with greases, oils and organic degradation products of the organic bath additives employed, have been found to cause a progressive deterioration of the quality of the electrodeposit and to greatly restrict the permissible bath operating parameters requiring relatively stringent control to maintain high quality electrodeposits. The progressive deterioration of the bath is typically evidenced by electrodeposits which contain white, blotchy or black areas that form in the intermediate and low current density areas of the conductive substrate being plated. Additionally, adverse physical properties of the electrodeposit is also evidenced, including high stress, poor ductility and inadequate adhesion in some instances.
In accordance with the present invention, an improved bath composition and process is provided which overcomes the detrimental effects of bath contamination during operation, which permits operation at a higher pH level to achieve excellent brightness and leveling, which permits more latitude in the parameters of bath control, and which facilitates the attainment of the desired high quality nickel-iron alloy deposit on a consistent basis. The invention further contemplates the use of a particular replenishing agent for conventional nickel-iron baths which when employed in controlled amounts is effective to achieve the aforementioned benefits. Additionally, the invention also contemplates a process for rejuvenating conventional nickel-iron electroplating baths which have been rendered inefficient or ineffective to achieve the desired high quality deposits due to the accumulation of contaminants therein by the controlled addition of a rejuvenating agent effective to restore the electroplating bath to its original operating efficiency.